This section is from the book "Leaching Gold and Silver Ores. The Plattner And Kiss Processes: A Practical Treatise", by Charles Howard Aaron. Also available from Amazon: Leaching Gold And Silver Ores.
196. There are two methods by which the free sulphur may be recovered from the precipitate. The first, introduced, it is believed, by Ottokar Hofman, consists in subjecting the mass to heat, in a retort, and condensing the sublimed sulphur. The second, original with myself, and which seems preferable, is as follows:
The unwashed precipitate is placed in a vat with water, boiled by means of a jet of steam, and slaked lime carefully added.
The free sulphur combines with the lime, in the manner already described, producing at once the precipitating solution of calcium polysulphide, and much more quickly than when the fresh sulphur is used. The boiling can be done in a filter vat, and when finished the clear solution can be drawn off. The precipitate is washed by passing hot water through it, dried and roasted as usual. Three-fourths or more of the sulphur is thus recovered for re-use.